The press briefing came a day after Prime Minister Pedro Sanchez, who wants to abolish prostitution altogether as does his executive, said the labour ministry had launched proceedings to challenge the union's existence in court.

Sex work is tolerated in Spain -- neither illegal nor regulated -- but Sanchez came to power in June with a strongly feminist agenda promising to fight the exploitation of women.

On Friday, government spokeswoman Isabel Celaa said "this government won't in any way allow a sex workers union."

Labour Minister Magdalena Valerio told reporters Thursday she was shocked by the fact such a union had been approved.

"As a minister and member of a feminist government, I would never have given the OK for this to be published in the official state gazette," she said.

Valerio added this has been one of "the biggest" upsets in her life.

Sex work is tolerated in Spain -- neither illegal nor regulated -- but the government of PM Pedro Sanchez came to power in June with a strongly feminist agenda promising to fight the exploitation of women. APP/AFP